Transparent substrate provided with a stack of thin layers

ABSTRACT

An insulated double glazing having the following layers in the following order: first dielectric layer, first layer with infrared reflection properties, second dielectric layer, second layer having infrared reflection properties, and third dielectric layer. The thickness of the first layer with infrared reflection properties is 50% to 64% of that of the second layer having infrared reflection properties.

This application is a Continuation of application Ser. No. 08/903,976Filed on Jul. 31, 1997, now U.S. Pat. No. 6,042,934, which is acontinuation of Ser. No. 08/622,619, filed Mar. 26, 1996 now abandoned,which is a continuation of Ser. No. 08/288,007, filed Aug. 10, 1994, nowabandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to transparent and in particular glass substratescovered with a stack of thin layers incorporating at least one metallayer able to reflect solar radiation and/or infrared radiation ofconsiderable wavelength.

The invention also relates to the use of such substrates for themanufacture of solar protection or control and/or thermal insulationglazings. These glazings are used both for equipping buildings andvehicles, with a particular aim of reducing air conditioningrequirements and/or reducing excessive overheating resulting from theever-increasing size of the glazed surfaces in car bodies.

2. Discussion of the Background

A known layer stack type for giving solar protective properties tosubstrates is constituted by at least one metal layer, such as a silverlayer, which is placed between two dielectric material layers of themetal oxide type. This stack is generally obtained by a succession ofdeposits carried out by a method using a vacuum such as magneticfield-assisted cathodic sputtering.

Thus, patent application WO 90/02653 discloses a laminated glazingintended for cars and whose outermost glass substrate with respect tothe vehicle body is provided with a stack of five layers on its innerface in contact with the thermoplastic material interlayer. This stackconsists of two silver layers intercalated with three zinc oxide layers,the silver layer closest to the outer substrate carrying the stackhaving a thickness slightly exceeding that of the second silver layer.

The laminated glazings according to said application are used aswindscreens, which explains why they have very high light transmissionvalues T_(L) of approximately 75%, in order to meet the safety standardsin force and therefore have a relatively high solar factor value SF. (Itis pointed out that the solar factor of a glazing is the ratio betweenthe total energy entering the room through said glazing and the incidentsolar energy).

The object of the invention is to develop a transparent substratecarrying a stack of thin layers having two layers which reflectradiation in the infrared and which are more particularly of a metallictype, so that they have a high selectivity, i.e. the highest possibleT_(L)/SF ratio for a given value of T_(L), while ensuring that saidsubstrate has an aesthetically satisfactory visual appearance inreflection.

SUMMARY OF THE INVENTION

Accordingly one object of the invention is to provide a transparentsubstrate, particularly of glass and having multiple thin layers, onwhich are successively deposited a first dielectric material layer, afirst layer having infrared reflection properties and in particularbased on metal, a second dielectric material layer, a second layerhaving infrared reflection properties, particularly based on metal, andfinally a third dielectric material layer. According to the invention,the thickness of the first layer having infrared reflection properties,i.e. that closest to the carrying substrate, corresponds to about50-80%, particularly 55 to 75% and preferably 60-70% of the thickness ofthe second layer having infrared reflection properties. An advantageousexample corresponds to a thickness of the first layer corresponding toabout 65% of the second.

This great asymmetry in the thicknesses of the layers having infraredreflection properties makes it possible to advantageously modify thevalues of T_(L) and SF so as to obtain glazings having a goodselectivity, i.e. a good compromise between the need for transparencyand that of providing an optimum protection against solar heat rays.

Moreover, the choice of such an asymmetry leads to another advantageousconsequence. Not only does it make it possible to obtain glazings havingan attractive visual appearance, particularly in reflection, i.e. havinga neutral “whitewashed” coloring, but the visual appearance remainsvirtually unchanged regardless of the angle of incidence with which theglazing is observed. This means that an external viewer of the facade ofa building, entirely equipped with such glazings, does not have a visualimpression of a change of shade as a function of the location on thefacade at which he is looking. This characteristic of appearance inuniformity is very interesting, because it is presently highly desiredby building architects.

Moreover, the visual appearance of the glazing, both in reflection andtransmission, can also be refined and controlled by an adequateselection of the materials and the relative thicknesses of the threedielectric material layers.

Thus, according to a non-limiting first embodiment of the invention, theoptical thickness of the first dielectric material layer is chosen to beabout equal to that of the third dielectric material layer. About equaloptical thicknesses is to mean within 10%, preferably within 5%, morepreferably within 2.5% of the thickness of the other layer. The opticalthickness of the second dielectric material layer is then advantageouslychosen above or equal to 110% of the sum of the optical thicknesses ofthe two other dielectric material layers (i.e. the first and thirdlayers) and preferably corresponding to about 110 to 120% of said sum.

In a second embodiment relating to the relative thicknesses of thedielectric material layers, which is advantageous, consists of choosingan optical thickness of the first dielectric material layer whichexceeds the optical thickness of the third dielectric material layer.Thus, the optical thickness of the first dielectric material layer cancorrespond to at least 110% of the optical thickness of the thirddielectric material layer, particularly at least 110 to 140%, especially115 to 135% and preferably about 125% of the optical thickness of thelatter. In the case of the drawing, it is recommended that the opticalthickness of the second dielectric material layer be chosen to be aboutequal to the sum of the optical thicknesses of the two other dielectricmaterial layers. About equal optical thicknesses is to mean within 10%,preferably within 5%, more preferably within 2.5% of the thickness ofthe other layer.

In the first and second embodiments cases, such relative proportionsbetween the optical thicknesses of the dielectric material layers makesit possible to obtain colors in reflection and even also intransmission, which are aesthetically appreciated and in particular blueand green.

However, the second embodiment has an additional advantage compared withthe first embodiment, to the extent that it optimizes the“non-sensitivity” of the complete stack to thickness variations of thedifferent dielectric material layers forming it. This means that slightthickness variations of one of the dielectric material layers in thestack does not lead to flagrant appearance deficiencies betweenindividual glazings or on the surface of the same glazing. This is veryimportant from the industrial standpoint, where manufacture takes placeof glazings having a considerable size and/or in large numbers with theaim of retaining appearances and performance characteristics which areas uniform as possible between individual glazing batches, particularlywithin individual zones of the same glazing.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 displays the positional relationship of a transparent substrateaccording the present invention, where the relative thicknesses of thelayers is not indicated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In terms of choice of material for said thin layer stack, it ispreferred to place on each of the layers having infrared reflectionproperties and in particular those layers based on metal, a thin“barrier” layer, particularly when the dielectric layer above the layerhaving infrared reflection properties is deposited by reactive cathodicsputtering in the presence of oxygen. Therefore said barrier layersprotect the metal layers in contact with the oxygen and themselvespartly oxidize during the deposition of the upper dielectric layer.Suitable “barrier layers” are preferably based on a tantalum, titaniumor nickel-chromium alloy and have a thickness of 1 to 3 nanometers.

With regards to the layers having infrared reflection properties, goodresults are obtained with silver layers.

The dielectric material layers are preferably based on tantalum (V)oxide, zinc oxide, tin (IV) oxide, niobium (V) oxide, titanium (IV)oxide or a mixture of certain of these oxides. It is also possible forone of the layers to be constituted by two superimposed oxide sublayers,one being of tin (IV) oxide and the other of an oxide making it possibleto improve the wetting of the layers having infrared reflectionproperties, such as tantalum (V) oxide or niobium (V) oxide inaccordance with French patent application 93/01546 filed on Feb. 11,1993 and European patent application 94 400 289.8 filed on Feb. 10,1994, or titanium (IV) oxide.

Each of the oxides given above has advantages. Thus, tin (IV) oxide andzinc oxide have high deposition speeds when deposited by reactivecathodic sputtering, which is of great interest industrially. However,tantalum (V) oxide or niobium (V) oxide make it possible to obtain anincreased durability of the tack with respect to mechanical or chemicalaggressions and in particular lead to a better wetting of the silverlayers when they are positioned below the latter. Mixed oxides can offera compromise between the deposition rate and the durability and thesuperimposing of two oxide layers reconciles in an optimum manner thecost of the starting materials and a wettability of the silver layers.

There is also an additional advantage associated with the use oftantalum (V) oxide. A glazing provided with a stack having such adielectric material can be blue both in reflection and in transmission,which is appreciated from the aesthetic standpoint and is alsosurprising, because usually, in transmission, the color obtained iscomplimentary of that obtained in reflection, when the thin layers inquestion are only slightly or non-absorbent.

A suitable substrate material is preferably a conventional transparentglass substrate used in optical applications, particularly such asautomotive window glass and building window glass.

A preferred embodiment of the stack according to the invention consistsof choosing a thickness of 7 to 9 nanometers for the first metal layerand a thickness of 11 to 13 nanometers for the second. Preferably theoptical thickness of the first and third dielectric material layers isbetween 60 and 90 nanometers, their geometrical thickness being inparticular between 30 and 45 nanometers. The optical thickness of thesecond layer is between 140 and 170 nanometers, while its geometricalthickness is between 70 and 80 nanometers. It is pointed out that theoptical thickness, as it refers to the dielectric material layers, isdefined in a conventional manner by the product of the real geometricalthickness of the dielectric material layer and the refractive index ofthe dielectric material forming it. As a function of the envisaged oxidetype, the index varies between 1.9 and 2.1 for tin (IV) oxide ortantalum (V) oxide and to about 2.3 for oxides of the niobium (V) oxidetype.

The transparent substrate coated with the stack according to theinvention can advantageously be incorporated into a multiple glazing andin particular as one of the glass layers of an insulating doubleglazing. In the latter case, the double glazing has a light transmissionvalue (T_(L)) between 60 and 70% and a solar factor SF of 0.32 to 0.42,which make it completely suitable for use in buildings. Moreover, itpreferably has in reflection, a virtually unchanged visual appearance,no matter what the vision incidence angle, the values of a*, b* in thecolorimetry system (L, a*, b*, c*) remaining unchanged, below 3 andnegative.

It can also form part of a laminated glazing with, in particular, alight transmission of about 70%.

Other features of the invention will become apparent in the course ofthe following descriptions of the exemplary embodiments which are givenfor illustration of the invention and are not intended to be limitingthereof.

In all the examples, the successive deposits of the layers of the stackwas performed by magnetic field-assisted cathodic sputtering, however,any other deposition procedure can be practiced provided that it permitsa good control and monitoring of the thicknesses of the layers to bedeposited.

The substrates on which the stacks are deposited were 4 mm thicksoda-lime-silica glass substrates, except for Examples 7 to 10, wherethe substrates were 6 mm thick. In double glazings, they were assembledwith another substrate identical to the first, but in the blank state,by means of a 10 mm space of gas, except for the Examples 7 to 8, wherethere was a 12 mm space of gas.

FIG. 1 shows the stack according to the invention and does not respectproportions with respect to the thicknesses of the layers so as tofacilitate understanding. It is possible to see the previously definedsubstrate 1, surmounted by a first tin (IV) oxide or tantalum (V) oxidedielectric material layer 2, a first silver infrared reflective layer 3,a titanium or Ni—Cr alloy barrier alloy (partly oxidized) 4, a secondtin (IV) or tantalum (V) oxide dielectric material layer 5, a secondsilver infrared reflective layer 6, another barrier alloy layer 7identical to the first barrier alloy layer 4 and finally a lastdielectric material layer 8 of one of the same oxides.

A suitable deposition apparatus comprises at least one sputteringchamber equipped with cathodes having targets made from appropriatematerials under which the substrate 1 successively passes. Suitabledeposition conditions for each of the layers are as follows:

The silver-based layers 3, 6 may be deposited with the aid of a silvertarget, under a pressure of 0.8 Pa in an argon atmosphere, the layers 2,5 and 8, when based on SnO₂, may be deposited by reactive sputteringwith the aid of a tin target under a pressure of 0.8 Pa and in anargon/oxygen atmosphere, including 36 vol. % oxygen.

The layers 2, 5, 8, when based on Ta₂O₅ or Nb₂O₅ may be deposited byreactive sputtering respectively with the aid of a tantalum target or aniobium target under a pressure of 0.8 Pa and in an argon/oxygenatmosphere, whereof about 10 vol. % is oxygen.

The layers 4, 7 based on Ni—Cr or titanium may be deposited with the aidof a nickel-chromium alloy or titanium target under the same pressureand in an argon atmosphere.

The power densities and travel speeds of the substrate 1 may be adjustedin a known manner so as to obtain the desired layer thicknesses.

In all the following Examples, with the exception of the last, tantalum(V) oxide is chosen as the dielectric material for the layers 2, 5 and8.

EXAMPLES 1 to 5

Examples 1, 2 and 5 are comparative examples to the extent that in thesethree cases, the silver layers 3 and 6 have either virtually identicalthicknesses (Example 1) or different thicknesses, but where theasymmetry is reversed compared with that of the invention (Examples 2and 5). Examples 3 and 4 are in accordance with the teachings of thepresent invention.

The following Table 1 gives for each of the Examples the nature andthicknesses (in nanometers) of the layers of the stack in question. Thebarrier layers 4 and 7 are designated Ni—Cr, knowing that they are infact partly oxidized once all the layers have been deposited.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 5 Glass (1) — — — — — Ta₂O₅ (2) 36.534.5 32 32 32 Ag (3) 10 11.5 8 8 12 Ni-Cr (4) 2 2 2 3 2 Ta₂O₅ (5) 77.594.5 77.5 72.5 77.5 Ag (6) 11 8 12 12.5 8 Ni-Cr (7) 2 2 2 2 2 Ta₂O₅ (8)33.5 35 33.5 32 33.5

The following Table 2 indicates for each of the above Examples the lighttransmission value T_(L) as a percentage, the solar factor SF calculatedaccording to DIN standard 67507 (Appendix A 233) as a percentage, thedominant wavelength values lambda-dom-t nanometers and the associatedcoloring purity (p.t.) as a percentage. Also indicated are the lightreflection values R_(L) as a percentage, the dominant wavelength inreflection lambda-dom-r and the reflection purity (p.r.) as apercentage, the colorimetry measurements having been performed undernormal incidence. All the measurements relate to the substrate fitted asa double glazing, with reference to the illuminant D₆₅.

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 T_(L) 69 66 70 61 62 SF 42 42 4238 38 Lambda-dom-t 493 489 498 490 478 p.t. 2 5 2 4 6 R_(L) 12 19 10 1021 Lambda-dom-r 561 641 486 487 574 p.r. 3 9 3 6 35

The following Table 3 gives the values of the dominant wavelength inreflection lambda-dom-r, the reflection purity p.r. for some of thepreceding examples (the substrate still being installed in a doubleglazing), but on this occasion measured with an angle of incidentrelative to the perpendicular to the plane of the substrate ofrespectively 60 and 700.

TABLE 3 Ex. 1 Ex. 2 Ex. 3 Ex. 5 Lambda-dom-r (60°) 470 569 480 571 p.r.(60°) 5.4 3 4.68 8 R_(L) (60°) 19 28 20 27 Lambda-dom-r (70°) 462 490481 −498 p.r. (70°) 4.3 4 3.0 0.8 R_(L) (70°) 32 39 34 36

Other colorimetry measurements with incidence angles 0° and 60° wereperformed, on this occasion in the system (L*, a*, b*), for Examples 2and 3, as well as for example 5, which is in all points identical toexample 3, except that the silver layers 3 and 6 were reversed andconsequently falling outside the conditions recommended by theinvention. Table 4 groups the values of a* and b*, as well as c* calledsaturation and equal to the square root of the sum of the squares of a*and b*.

TABLE 4 Ex. 2 Ex. 3 Ex. 5 a* (0°) 12.2 −0.9 −2.2 b* (0°) 3.1 −3.1 22 c*(0°) 12.6 3.2 22.1 a* (60°) −1 −0.9 −1.7 b* (60°) 2 −3 6 c* (60°) 2.23.13 6.2

The following conclusions can be drawn from this information.

Under a normal incidence angle, i.e., giving different thicknesses tothe silver layers and solely in such a way that the silver layer closestto the substrate is much thinner, enables the obtaining of glazingswhich are blue in reflection.

It should be noted that the glazings according to the invention,particularly when the chosen dielectric is tantalum (V) oxide, are alsoblue in transmission.

Thus, only Examples 3 and 4 have lambda-dom-r values of approximately486 nanometers and lambda-dom-t values of 490 nanometers, according toTable 2. However, the glazings of Examples 1 and 5 have in reflection ayellow shade, whereas that of Example 2 is a red-purple shade.

In addition, the coloring purity in reflection p.r. of Example 2, closeto 10%, is much higher than that of Examples 3 and 4 according to theinvention. (This value of p.r. is even higher for Example 5).

Moreover, the glazings of Examples 3 and 4 according to the inventionhave a good selectivity of at least 1.6 or 1.7 with a solar factorremaining equal to or below 42%.

Thus, the obtaining of a favorable colorimetry according to theinvention is not to the detriment of the solar protection performancecharacteristics of the glazings in question.

Tables 3 and 4 make it possible to evaluate the uniformity of theappearance in reflection of the glazings according to certain of thepreceding examples. Table 3 shows that the glazing according to Example3 in accordance with the invention retains a blue color in reflection,with a lambda-dom-r value remaining virtually constant towards 486 at 0°to 481 at 70°, the purity in reflection also remaining very moderate.

However, the glazing according to Example 1, where the silver layersapproximately have the same thickness, passes from a yellow color inreflection under normal incidence to a blue and then violet color at 60°and then 70°.

Table 4 confirms that only Example 3 according to the invention makes itpossible to maintain an identical colored appearance in reflection nomatter what the incidence angle, because the values of a* and b* remainvirtually unchanged, as does the saturation c*.

This is not the case with the glazings of Examples 2 and 5, where thevalues of a* and b* change completely as a function of the incidenceangle. Thus, the value of a* passes, for the glazing of Example 2, froma very high positive value of 12.2 at 0° to a very low negative value of−1 at 60°.

Thus, only the examples according to the invention reconcile theselectivity and appearance uniformity.

EXAMPLES 6 and 7

These two examples use as the dielectric material tin (IV) oxide and nottantalum (V) oxide and use for the barrier layers either titanium(Example 6) or Ni—Cr (Example 7).

The following Table 5 indicates the thickness values in nanometers usedfor each of the stack layers:

TABLE 5 Ex. 6 Ex. 7 Glass (1) — — SnO₂ (2) 34 32 Ag (3) 8 8 Ti or Ni-Cr(4) 1 1.5 SnO₂ (5) 77 74.5 Ag (6) 12 11.6 Ti or Ni-Cr (7) 1 1.5 SnO₂ (8)35 33

The thus coated substrates were installed in double glazings, asexplained hereinbefore. The photometric measurements on the doubleglazings appear in Table 6 (measurements under normal incidence).

TABLE 6 Ex. 6 Ex. 7 T_(L) 66 65 SF 38 39 R_(L) 10.4 9.4 lambda-dom-r 511484 p.r 2 2 a* — −0.5 b* — −1.1

These glazings, like those of Examples 3 and 4, reveal no significantmodification of their visual appearance in reflection, no matter whatthe measurement angle. In reflection they have a color towards thegreens for Example 6 and towards the blues for Example 7, but thesecolors remain very neutral, in view of the very low purity valuesassociated therewith.

Laminated glazings incorporating the covered substrates of the stackaccording to the invention retain the favorable colorimetry observed inthe case of monolithic substrates or substrates installed in doubleglazings.

Thus, the substrate covered with the stack according to Example 3 wasassembled with another substrate of the same type, but without a layer,using standard, 0.3 mm thick, polyvinyl butyral film.

The following Table 7 give for said laminated glazing the alreadyexplained values of T_(L), p.t. lambda-don-t, a* and b* in connectionwith the appearance in transmission, as well as the corresponding valuesR_(L), p.r. lambda-don-r, a* and b* concerning the appearance inreflection on the side of the substrate provided with the stack oflayers (same units as hereinbefore).

TABLE 7 T_(L) 70 p.t. 1.2 lambda-dom-t 502 a* −3.27 b* 0.52 R_(L) 14p.r. 8 lambda-dom-r 483 a* −2.2 b* −4.4

Table 7 shows that the incorporation of substrates covered in accordancewith the invention in a laminated glazing structure leads to nodeterioration of their aesthetic colorimetry. The thus obtainedlaminated glazing remains in the blues or greens, both in transmissionand in reflection.

Examples 3, 4 and 6 according to the invention relate to its “firstvariant” mentioned hereinbefore, i.e., respecting a choice of relativethicknesses between the three oxide layers 2, 5 and 8 which is specificand approximately as follows. The thickness of the layer 2 isapproximately as follows. The thickness of the layer 2 is approximatelyequal to that of the layer 8 and the thickness of the layer 5 (in thecenter) is slightly greater than the sum of the thicknesses of the twoother layers 2 and 8 (in these examples reference can be made to eitherthe geometrical thickness or the optical thickness, because the threelayers are made from the same oxide).

The “second variant” according to the invention will now be illustratedby the following example and more particularly Example 8. In thisvariant, the thickness ratios between the oxide layers 2, 5 and 8 areslightly modified, the optical thickness of the layer 2 beingsignificantly (25%) higher than that of the layer 8. The opticalthickness of the layer 5 (or the sum of the optical thicknesses of thedifferent sublayers forming it) is here approximately equal to the sumof the optical thicknesses of the two other layers 2 and 8.

EXAMPLE 8

The substrate according to Example 8 is covered with a stack similar tothat described for Example 7, the layers 2, 5 and 8 being of tin (IV)oxide, but of different thicknesses.

The following Table 8 gives the thickness values in nanometers of allthe layers of the stack in question.

TABLE 8 Ex. 8 Glass (1) — SnO₂ (2) 41 Ag (3) 8 Ni-Cr (4) 1.5 SnO₂ (5)74.5 Ag (6) 12 Ni-Cr (7) 1.5 SnO₂ (8) 33

The substrate is fitted in a double glazing. The photometricmeasurements performed on the double glazing are given in table 9(measured under normal incidence).

TABLE 9 Ex. 8 T_(L) 65 SF 39 R_(L) 9.1 Lambda-dom-r 486 p.r. 1 a* −0.7b* −0.5

Comparing these results with those obtained in Example 7, it can be seenthat identical values of T_(L) and SF are obtained. The appearance inreflection is also in the blues, with an even more neutral color,because the purity is approximately 1% and the values of a* and b* areboth well below 1. Another advantage of the stack type according toExample 7 is that it more easily permits slight thickness variations inthe stack layers, from one point to the other of the substrate, withoutgiving rise to noticeable modifications of its visual appearance.

Thus, on performing measurements of a* and b* in reflection at differentpoints of the substrate according to Example 8 fitted in a doubleglazing, it is found that the value differences remain below 1, i.e.differences which cannot be noticed by the human eye, even if each ofthe layers has local thickness variations of +/−4%. This is veryimportant from the industrial standpoint, because it makes it moreeasily possible to obtain glazings which are both uniform, i.e. havingno local appearance modifications, and reproducible, i.e. having anidentical appearance between individual glazings or between individualglazing batches. This means that for a given production line, which hasits own performance limits, particularly with regards to the regularityof the layers obtained, such a stack will be less “sensitive” thanothers to thickness variations of the layers imposed by the line andwill consequently have a better optical quality.

Conversely, on imposing a given optical quality, it is possible withthis type of stack, to use a production line under less draconianconditions or to use a production line having slightly inferiorperformance characteristics.

It is also advantageous from the industrial standpoint for the layer 5to have a thickness roughly equal to the sum of the thicknesses of thelayers 2 and 8. Thus, it is then sufficient to use two targets, here oftin, whereof it is possible to regulate the power values supplied “onceand for all” in their respective deposition chambers. The layer 2 isthen obtained by the passage of the substrate under one of the targetswith settings permitting the deposition of a predefined adequatethickness. In the same way, the layer 8 is obtained by the passage ofthe substrate under the second target with settings make it possible toobtain the deposition of a previously defined adequate thickness. Thelayer 5 is obtained by consecutive passages of the substrate under eachof the targets, so that on the substrate are superimposed a layerthickness corresponding to that of the layer 2 or 8 and then a layerthickness corresponding to that of the layer 8 or 2, i.e. the sum of thethicknesses of these two layers is formed without calling on a thirdtarget.

EXAMPLES 9 to 12

The aim of these examples is to optimize the wettability and thereforethe performance characteristics of at least one of the silver layers.They follow the teaching of European patent application 94 400 289.8.

In the case of Examples 9 and 10, the layers 2 and 8 are once again oftin (IV) oxide, but the layer 5 is subdivided into two superimposedbislayers, the first 5 being of tin (IV) oxide and the second 5 bis oftantalum (V) oxide (for Example 9) or niobium (V) oxide (for Example10). A thin metallic sublayer can be optionally provided below thesilver layer 6 and which is of NiCr or Sn.

In the case of Examples 11 and 12, the layer 2 is also subdivided intotwo superimposed sublayers, the first 2 being of tin (IV) oxide and thesecond 2 bis of tantalum (V) oxide (for Example 11) or niobium (V) oxide(for Example 12). An optional, thin metallic sublayer can be providedbeneath the silver layer 3.

Thus, in the case of Examples 9 and 10, the wettability of the secondsilver layer 6 is optimized, whereas in the case of Examples 11 and 12,the wettability of the two silver layers 3 and 6 is optimized.

Table 10 gives the thicknesses in nanometers of the layers present.

TABLE 10 Ex. 9 and 10 Ex. 11 and 12 Glass (1) — — SnO₂ (2) 41 30-31Ta₂O_(5 or Nb) ₂O₅ (2 bis) 0 10 Ag (3) 8 8 Ni-Cr (4) 1.5 1.5 SnO₂ (5) 6464 Ta₂O_(5 or Nb) ₂O₅ (5 bis) 10 10 Ag (6) 12 12 Ni-Cr (7) 1.5 1.5 SnO₂(8) 33 33

There is a slight improvement to the solar control performancecharacteristics of the stacks. Moreover, the use of oxides known fortheir hardness, such as tantalum or niobium (V) oxide, helps to optimizethe durability of the overall stack and in particular its mechanicaldurability. This mechanical strength increase is particularly pronouncedfor Examples 11 and 12.

In conclusion, the glazings according to the invention have both a goodselectivity of about 1.70, a uniform visual appearance which isattractive to the eye (particularly a blue or green color in reflectionand optionally also in transmission), as well as a range of lighttransmission values making them suitable for use as solar controlglazings in buildings, particularly in the form of double glazings, thestack of thin layers preferably being on face 2 (the faces areconventionally numbered from the outside to the inside of the room inquestion).

The substrates covered with layers according to the invention can alsobe used with advantage for producing laminated glazings.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

This application is based on French patent applications FR 93/09917filed in France on Aug. 12, 1993 and FR 94/02723 filed in France on Mar.9, 1994, the entire contents of which of each are hereby incorporated byreference. What is claimed as new and desired to be secured by LettersPatent of the United States is:

What is claimed is:
 1. An insulating double-glazing having a lighttransmission (T_(L)) between 60 and 70% and a solar factor of 0.32-0.42,and a color in external reflection in the blues or greens, whichcomprises: a) a first layer, and b) a second layer, which is atransparent substrate having multiple thin layers, comprisingsuccessively: i) a first dielectric layer on said substrate; ii) a firstlayer having infrared reflection properties on said layer i); iii) asecond dielectric material layer on said layer ii); iv) a second layerhaving infrared reflection properties on said layer iii); and v) a thirddielectric material layer, wherein a thickness of said first layerhaving infrared reflection properties is 60-70% of said second layerhaving infrared reflection properties.
 2. The insulating double-glazingof claim 1, wherein an optical thickness of said second dielectricmaterial layer of said second layer (b) is equal to or greater than 110%of the sum of the optical thicknesses of said first and third dielectricmaterial layers of said second layer (b).
 3. The insulatingdouble-glazing of claim 2, wherein the optical thicknesses of the firstdielectric material layer and said third dielectric material layer areabout equal.
 4. The insulating double-glazing of claim 1, wherein theoptical thickness of said first dielectric material layer is greaterthan the optical thickness of the third dielectric material layer, andwherein the optical thickness of the first layer corresponds to at least110% of the optical thickness of the third layer.
 5. The insulatingdouble-glazing of claim 4, wherein the optical thickness of said seconddielectric material layers is about equal to the sum of the opticalthicknesses of the first and third dielectric layers.
 6. The insulatingdouble-glazing of claim 1, wherein each of said layers of said secondlayer (b) having infrared reflection properties is surmounted by apartly oxidized barrier metal layer.
 7. The insulating double-glazing ofclaim 1, wherein each of said layers of said transparent substratehaving infrared reflection properties contains silver.
 8. The insulatingdouble-glazing of claim 1, wherein at least one of said dielectricmaterial layers on said transparent substrate is a material selectedfrom the group consisting of tantalum (V) oxide, tin (IV) oxide, zincoxide, niobium (V) oxide, titanium (IV) oxide and mixtures of saidoxides.
 9. The insulating double-glazing of claim 1, wherein each ofsaid dielectric material layers or said transparent substrate is amaterial selected from the group consisting of a first layer of tin (IV)oxide surmounted by a second layer of tantalum (V) oxide, niobium (V)oxide or titanium (IV) oxide.
 10. The insulating double-glazing of claim1, wherein the thickness of said first layer having infrared reflectionproperties is between 7 and 9 nanometers.
 11. The insulatingdouble-glazing of claim 1, wherein the thickness of said second layer ofsaid transparent substrate having infrared reflection properties isbetween 11 and 13 nanometers.
 12. The insulating double-glazing of claim6, wherein said barrier metal layer contains a material selected fromthe group consisting of titanium and nickel-chromium alloy.
 13. Aninsulating double-glazing having a light transmission (T_(L)) between 60and 70% and a solar factor of 0.32-0.42, and a color in externalreflection in the blues or greens, which comprises: a) a first layer;and b) a second layer thereon, which is a transparent rigid substratehaving multiple thin layers thereon, comprising successively: i) a firstdielectric material layer on said substrate; ii) a first layer havinginfrared reflection properties on said layer i); iii) a seconddielectric material layer on said layer ii); iv) a second layer havinginfrared reflection properties on said layer iii); and v) a thirddielectric material layer on said layer iv); wherein a thickness of saidfirst layer having infrared reflection properties is 50-64% of that ofsaid second layer having infrared reflection properties.
 14. Theinsulating double-glazing of claim 13, wherein an optical thickness ofsaid second dielectric material layer of said second layer (b) is equalto or greater than 110% of the sum of the optical thicknesses of saidfirst and third dielectric material layers.
 15. The insulatingdouble-glazing of claim 13, wherein the optical thicknesses of the firstdielectric material layer and said third dielectric material layer areabout equal.
 16. The insulating double-glazing of claim 13, wherein theoptical thickness of said first dielectric material layer is greaterthan the optical thickness of the third dielectric material layer, andwherein the optical thickness of the first layer corresponds to at least110% of the optical thickness of the third layers.
 17. The insulatingdouble-glazing of claim 16, wherein the optical thickness of said seconddielectric material layers is about equal to the sum of the opticalthicknesses of the first and third dielectric layers.
 18. The insulatingdouble-glazing of claim 13, wherein each of said layers of said secondlayer (b) having infrared reflection properties is surmounted by apartly oxidized barrier metal layer.
 19. The insulating double-glazingof claim 13, wherein each of said layers of said transparent substratehaving infrared reflection properties contains silver.
 20. Theinsulating double-glazing of claim 13, wherein at least one of saiddielectric material layers on said transparent substrate is a materialselected from the group consisting of tantalum (V) oxide, tin (IV)oxide, zinc oxide, niobium (V) oxide, titanium (IV) oxide and mixturesof said oxides.
 21. The insulating double-glazing of claim 13, whereineach of said dielectric material layers or said transparent substrate isa material selected from the group consisting of a first layer of tin(IV) oxide surmounted by a second layer of tantalum (V) oxide, niobium(V) oxide or titanium (IV) oxide.
 22. The insulating double-glazing ofclaim 13, wherein the thickness of said first layer having infraredreflection properties is between 7 and 9 nanometers.
 23. The insulatingdouble-glazing of claim 13, wherein the thickness of said second layerof said transparent substrate having infrared reflection properties isbetween 11 and 13 nanometers.
 24. The insulating double-glazing of claim18, wherein said barrier metal layer contains a material selected fromthe group consisting of titanium and nickel-chromium alloy.